1. Field of the Invention
This invention relates generally to lacing elongate members through sheet material, and in particular to an apparatus operable to lace a flexible line through sheet material of an indefinite length in a continuous operation. The apparatus is applicable for lacing flexible lines of metal, plastic, cord or other material through woven or knitted plastic sheet material, such as plastic shade cloth, and it will be convenient to hereinafter describe the invention in relation to that exemplary application. It is to be appreciated, however, that the invention is not limited to that application.
2. Description of the Related Art
Woven and knitted plastic shade cloth is mounted over skeletal frame structures to provide underlying plants with protective cover against adverse climatic conditions, particularly excess sun and wind. The shade cloth is often fixed taut to the frame structure by way of battens or plates nailed or otherwise fastened by way of battens or plates nailed or otherwise fastened to the structure. Such an arrangement is suitable where the shade cloth spans only short distances unsupported by the structure.
However, sometimes the shade cloth is required to cover large areas, such as orchards and nurseries and, as is usual for economic reasons in such arrangements, the frame structure is sparse so that the shade cloth must span large distances unsupported by the structure. Although the shade cloth can be drawn taut for initial fixing to the frame structure, the nature of the cloth material and its exposure to all environmental conditions, usually means that the cloth progressively sags across the unsupported distances. Moreover, the cloth may eventually tear away or dislodge from the frame structure so that its effectiveness is reduced.
In an effort to alleviate this problem, flexible lines of wire, plastic, cord, fabric and other suitable material have been laced through the shade cloth for extending over the span distances. Typically, lines can be laced along edge regions of the shade cloth. Those lines are then attached taut to the frame structure and thereby assist in supporting the shade cloth on the structure over their span distances. Moreover, when separate strips or other pieces of shade cloth are mounted adjacent one another on the frame structure, adjacent edge regions are sometimes overlapped and laced together with the flexible lines. This joining of the shade cloth pieces unifies the cloth against tearing or dislodgement, and generally improves the integrity of the protective cover given to the underlying plants.
Up to now the flexible lines have usually been manually laced through the shade cloth. That process is slow, tedious, prone to erratic lacing of the shade cloth, and costly.
Several machines have been developed for generally pleating and lacing various sheet materials other than shade cloth. Examples of these machines are disclosed in U.S. Pat. Nos. 4,811,873, 4,323,021, 3,767,091, 2,583,582, 2,551,808, 2,303,380 and 2,232,178.
These machines typically include a plurality of pleating rollers having intermeshing teeth, the sheet material being progressively fed through the intermeshing teeth which fold the material into pleats. One or more lacing needles are arranged with leading ends adjacent the intermeshing teeth so that, as the material is pleated, the pleats are impaled onto the leading ends and gathered on the needles.
The earlier machines, such as in U.S. Pat. No. 2,303,380, were usually discontinuous in operation, so that a length of sheet material was pleated onto the needles, and the machines then stopped to allow removal of that pleated material from the needles. However, more recent machines, such as in U.S. Pat. No. 4,811,873, operate to continuously pleat the sheet material and move it along the needles. Typically, such machines have their needles arranged so that lacing threads are passed through eyes at one end of the needles. The pleated material can then be progressively removed from the needles so as to be laced onto the threads.
None of these machines are intended or adapted for lacing a flexible line along a longitudinal edge region of shade cloth. Indeed, most of the machines are intended to lace sheet material with a series of threads spaced apart across the material so that the entire material can be smocked. A corollary to this is that those machines generally operate to retain the pleats within the sheet material; at least they do not tend to unpleat the material following lacing as is required with the laced shade cloth.
Moreover the lacing needles in these machines are fixed in position by means of needle holders connected to trailing ends of the needles, or supported in circumferential grooves provided in the pleating rollers. Neither of these arrangements are satisfactory for fast lacing of shade cloth. In particular, such arrangements do not ensure that the pleated sheet material is stripped clear of the needles and thus avoids bunching of pleats on the needles immediately downstream of the pleating rollers.
Thus, these prior art machines are not suitable for lacing longitudinal edge regions of sheet material, such as shade cloth.